EP2056489B1 - Method for transmitting multiplexed rate-limited and push-to-talk voice communications - Google Patents

Description

The invention relates to digital voice telecommunication systems, of limited flow and half-wave type, used in civil and military air traffic control systems to provide phonic links between air traffic control operators and flight deck members. airplanes under control.

The sound chain of these telecommunications systems includes, with reference to the figure 1 a control center 1 geographically well located, whose functions can be similar to those of a PABX (Private Automatic Branch eXchange or private branch exchange), radio centers 2 in analog radio link 5 with aircraft 4 whose flight is to control, the control center 1 and the various radio centers 2 being connected by a conventional digital communication network ISDN 3 (Integrated Services Digital Network) based on B channels at 64 kilobits per second.

The radio centers 2 are thus located in geographical outport of the control center 1, for example several hundred kilometers away, and are appropriately distributed to allow the coverage of an aerial area to control.

The radio links 5 are of the "half-way" type. In the absence of any emission from a control operator, the ground audio link is established in the direction of the airplane - control center.

When the controller wishes to speak to the pilot, he sends a signal of alternation, which commands at the radio centers 2 to transmit the voice data received from the center 1 by the ISDN network to the aircraft 4 on a given aircraft frequency , here in VHF or UHF, after digital - analog conversion.

Conversely, if the pilot transmits a signal from the aircraft 4, he commands the radio centers 2 at his radio range to receive the analog voice signals that he has transmitted at the same frequency as above and to retransmit them after analogue to digital conversion on the ISDN network to the control center 1, accompanied by an "airplane call".

In both cases, the signals or digital data of alternate or aircraft call are joined to the digital voice signals or data. and are, in part, service data contributing to call management at the control center level and at the radio center level.

Thus at any time, a set of aircraft can be controlled thanks, in part, to the processing of all voice and associated service data.

At the radio communication centers, the power of the reception signals resulting from the signals transmitted at the level of the aircraft is raised and the corresponding measurement is joined to the service data transmitted on the ISDN network to the control center.

It is the control center which finally selects, for a given plane, the phonic signals to be processed among those coming from the various radio centers. It chooses in real time the one with the highest reception quality and, consequently, associates with each aircraft in the controlled air zone the radio centers most likely to receive its signals (the closest, often).

Air traffic intensifying and communication capabilities being expensive, the plaintiff wanted to improve these communications.

Having found that the actual ISDN network throughput used to transmit voice communication was very excessive in relation to auditory quality requirements, the Applicant was able to pose the problem of optimizing the use of the network between the control center and radio stations leaving unchanged the radio communications between them and the aircraft cockpits.

And this is how she proposes her invention.

The invention thus relates to a method for transmitting voice communications of the limited rate and half-duplex type. as defined in claim 1.

The plaintiff, finding that a bit rate of 16 kilobits was sufficient to transmit via the network a voice radio communication aircraft, proposes to multiplex all aircraft communications without predetermining, as is usually done in a multiplexed communications system, or centers of the second level which must carry out the multiplexing or the constitution of the multiplexing groups.

For this purpose, software multiplexers are used which are controlled over time according to the needs of phonic communications with aircraft in transit in the area to be controlled.

Here, the group can hold n = 3 multiplexed voice communications, at a total rate of 48 kilobits per second, and service data multiplexed with the three voice communications at a rate of 16 kilobits per second, bringing to 64 kilobits per second the total bit rate of a multiplexed transmission of the group.

Said service data then contain at least the service data of the n multiplexed voice communications.

Preferably, the group of n stations of the third level is determined in the center of the first level at the same time as there is selected at least one center of the second level ensuring the soundtrack of said n positions of the third level.

Preferably again, it is at the first level that the center of the second level is selected to serve as a sounding post of a third level station, the selection being made according to the powers analog signals of said third level station received at the second level.

Advantageously, the power data of the analog signals received from the stations of the third level are transmitted to the center of the first level being included in said service data.

• la figure 1 est un schéma montrant la structure d'un système de télécommunications numériques vocales utilisé dans un système de contrôle aérien ;
• la figure 2 est un schéma par blocs fonctionnels d'un terminal comprenant le module de multiplexage de l'invention;
• la figure 3 est un schéma par blocs fonctionnels d'un récepteur exploitant le multiplexage selon l'invention ;
• la figure 4 est un chronogramme montrant le multiplexage d'un groupe de communications tel qu'utilisé entre les premier et second niveaux de communication selon l'invention et
• la figure 5 est un chronogramme de fonctionnement du système comportant le terminal et le récepteur des figures 2 et 3.

Other characteristics and advantages of the present invention will appear more clearly on reading the following description of the method according to the invention, with reference to the appended drawing in which:

• the figure 1 is a diagram showing the structure of a digital voice telecommunications system used in an air traffic control system;
• the figure 2 is a functional block diagram of a terminal comprising the multiplexing module of the invention;
• the figure 3 is a functional block diagram of a receiver operating the multiplexing according to the invention;
• the figure 4 is a timing chart showing the multiplexing of a communications group as used between the first and second communication levels according to the invention and
• the figure 5 is a chronogram of operation of the system comprising the terminal and the receiver of Figures 2 and 3 .

With reference to the figure 1 , the communication system 99 comprises, at a first communication level, a control center 1, generally designated VCS ("voice communication system"), at a second level of communication, several radio centers 2 connected to the control center by a communication network 3, PSTN or ISDN type, in the latter case on the B-channel, and, at a third level of communication, radio stations (not shown) of aircraft flight deck 4 under radio control of the center of control 1.

The control center 1 comprises a set of terminals 6, here called control operator stations (POC), structured around a switch 9, here a SAF 3000 equipment of the company communication in systems, connected to the network by a line interface 11.

The automatic switch 9 is here an intelligent switch allowing the POC 6 to be connected to the radio centers 2 and the radio centers 2 to the aircraft 4.

The auto-switch 9 selects the radio center 2 of the second level to serve as a voice deportment for each radio station plane 4 of the third level, the selection being made according to the comparison of the powers P of the analog signals individually for each of these radio stations 4 received at radio centers 2 of the second level. The powers P of the analog signals are transmitted to it as will be specified below.

The automatic switch 9 thus coordinates the established communications network by continuously selecting the radio centers 2 to put in phonic relation with this or that airplane 4 and by broadcasting the choices of use of the global network thus made to the POCs 6 and the radio centers. 2. Network usage choices and coordination choices are numerically coded and constitute service data.

The interface 11 additionally accumulates the functions of encryption / decryption. Each radio center 2 is connected to the public network 3 and the digital data transiting on the public network 3 are encrypted.

The POCs 6 are connected to the switch 9 by a computer network 10 of the intranet type.

Each radio center 2 comprises, connected to the module 11 'and thus to the network 3, a terminal 7 which is also an equipment SAF 3000 delivering and receiving its information to a radio terminal 8, here of the VHF or UHF type, itself connected radio 5 with the cockpits of aircraft 4 in radio range.

1. i) de récupération des données de service ci-dessus et celles issues de l'autocommutateur 9 et
2. ii) de commandes d'alternat, une interface numérique 23 et un bloc 12 de gestion temps réel du POC 6 et incluant un module 26 de séparation des données de phonie et des données de service et un module 25 d'assemblage des données de phonie et des données de service, un microphone 14 en sortie duquel est connecté un convertisseur analogique - numérique 27, convertissant la phonie analogique reçue du micro 14 en une suite d'octets d'intensité phonique représentatives d'une communication vocale, et un haut-parleur 15 en entrée duquel est inséré un convertisseur numérique - analogique 28 convertissant une suite d'octets d'intensité phonique représentatives d'une communication vocale reçue en des signaux de phonie analogique.

Each POC 6, with reference to the figure 2 , comprises a human-machine interface module 13 serving in particular to introduce service data and to perform an alternating command, a module 24

1. i) recovery of service data above and those from the switch 9 and
2. ii) alternate commands, a digital interface 23 and a real-time management block 12 of the POC 6 and including a voice data separation module 26 and service data and a voice data assembly module 25 and service data, a microphone 14 output of which is connected an analog-to-digital converter 27, converting the analog voice received from the microphone 14 into a series of octets of sound intensity representative of a voice communication, and a loudspeaker speaker 15 input of which is inserted a digital to analog converter 28 converting a series of octets of sound intensity representative of a received voice communication in analog voice signals.

The voice is sampled at 8 kilohertz and digitized with G.711 Recommendation A coding and gives speech octets at the sampling rate above.

Terminal 7, with reference to the figure 3 , symmetrically comprises a digital interface 34 in connection with the interface module 11 'receiving or transmitting digital voice and service data, a block 32 for real-time management of the sound and service data above including a module 35 for separating voice data and service data and a module 36 for assembling voice data and service data, a module 39 alternating switch, receiving its commands from the block 32, a transmission line 37, and commanding a line 38 for receiving the voice and alternate or aircraft call data, from the center 1 to the aircraft 4 or from the aircraft 4 to the center 1.

The switching command of the switch 39 results from the recognition, by the block 32, of the alternating signals present in service data joined to the voice data by the management block 12, which receives those of the automatic switch 9 as ordinarily , and airplane calls received by the radio module 8 and transmitted to the block 32 by the module 39.

The management module 12 receives the digital voice data from the microphone 14, retrieves the digital alternating signals from the interface 13, assembles these data and transmits them to the digital interface 23 for transmission on the intranet 10 to the switch 9, which transmits these data through the network 3 according to the switches it has established, as usual, to the radio centers 2.

The radio centers 2 in turn transmit the voice or voice data to the aircraft 4 via the radio link 5 and, to confirm this transmission, send back an acknowledgment signal from the radio module 8 and a feedback signal from the radio. listening to the control center 1.

The management module 32 receives the digital voice data and the digital signals of alternating and service data from the interface 34, separates these data from each other and uses the service data to transmit this data to the radio module 8 for radio transmission 5 to the designated aircraft 4 in the service data.

Here, between the first and second levels, multiplexes and demultiplexes the upstream communications of the POCs 6 to the aircraft 4 and the downward communications of the aircraft 4 to the POCs 6.

For this, the exchange 9, or the management module 23, constitutes groups Gk of n bidirectional communications, rising and falling, passing through the same radio center 2 capable of being multiplexed and transmitted simultaneously on the network 3.

The automatic switch 9 further comprises a multiplexing module 41 and a demultiplexing module 42, and each radio center 2 furthermore includes, in the module 34, multiplexing modules 52 and demultiplexing 51, of similar operation which will now be described, with reference to the figure 4 .

As the switch decides on the management of the network 3 and the radio links 5, it determines the n POC 6 or the n aircraft 4 of the same group Gk, that is to say the n POC 6 of the first level or n planes 4 of the third level which are attached to the same radio center 2 of the second level.

To optimize the use of the network 3, here n is chosen to be three. Thus, the multiplexing modules 41, 52 and demultiplexing modules 51 and 42 can be controlled over time as a function of the needs for sound communications with the POCs 6 or the aircraft 4 in transit in the area to be controlled.

Take the example of communications from POC 6 and to centers 2, but the description of reverse communications is similar.

The data of three POCs 6 consist of the service data S1, S2, S3 and voice data V1, V2, V3, that is to say in generalized designation: the POC k sends service data Sk and Vk voice data compressed at 16kb / s.

The voice data Vk are phonic octet streams (whose bits are denoted v _k ^{1, t} , ..., v _k ^{8, t} ) sampled in time (here of index t) at a speed of 8 kilohertz. It should be noted in passing that this speed corresponds to a transfer rate of 64 kilobits per second.

The module 41 will preserve this transfer rate globally for the transfer of the data from the three POCs 6 by temporally multiplexing them in frames of sixty bytes each.

A frame of this type has been represented at the bottom of figure 4 . Each byte of the frame has two bits of service data and two bits of voice data of each POC 6. For example, the first byte of the frame contains the first two bits s ₁ and s ₂ of the set of data Sk or data S as defined below, and the first two bits v _k ^1.1 and v _k ^1.2 of the data V k of each POC k.

• trois appels avion ou alternats,
• trois alarmes,
• trois informations de niveau de champ reçu (les puissances P),
• trois informations de chiffrement.

The data Sk are assembled into common service data S without difficulty since they are all intended for the same radio center 2. In the system under consideration, they comprise together the following data (in one or other of the communication directions):

• three plane or alternate calls,
• three alarms,
• three received field level information (the P powers),
• three encryption information.

All of these data are here in 90 bits, but a larger capacity of 120 bits has been provided. This capacity conditions the length of the frame used because, at the rate of two bits of data S by byte of the frame, it follows that it must have a packet Pk of 60 bytes.

On the figure 4 these 60 bytes are represented by sub-packets of four multiplexed bytes numbered by the index j, j taking its values from 1 to 15. Indeed, a subpacket j contains the eight bits v _k ^{1, j} to v _k ^{8, j} of each of the three Vk bytes issued simultaneously from the three POCs 6. The subpacket j also contains the eight bits s _8.j-7 , s _8.j-6 , s _8.j-5 , s _{8 .j-4} , s _8.j-3 , s _8.j-2 , s _8.j-1 , s _8.j extracted from the 120 bits of data S.

The module 41 comprises a software multiplexer arranged to assemble the service data S as above from the POCs 6 and to multiplex the data S and the data Vk as indicated above.

Similarly, in order to multiplex the communications transmitted by three aircraft 4, the module 52 comprises identical multiplexing software for assembling the service data S, as above, and multiplexing the data S and the voice data V generated by the converter. 38.

Conversely, the modules 42 and 51 are arranged to demultiplex the data S and the multiplexed voice data. The service data S resulting from the communications coming from the aircraft 4 are taken up by the module 32 and by the block 9 and the module 12 for subsequent processes, whose exploitation of the received field levels or that of the powers P of the analog signals received. , measured and transmitted by the radio module 8 in the service data.

It is this operation that enables the switch 9, by comparison of the powers P, to manage all the communications and to assign, over the course of communications, the best radio center 2 of the second level for each of the aircraft 4 of the third level.

Naturally, the service data S can be used only once a frame received completely, that is to say after sixty times 125 microseconds, or 7.5 milliseconds.

The operation of the system 99 during a two-way call and aircraft call exchange will now be detailed chronologically, with reference to the figure 5 , omitting, for simplicity, encryption operations.

• étape 100 : l'opérateur d'un POC 6 commande l'alternat pour parler à l'équipage d'un avion 4 ;
• étape 101 : le module 24 constitue une suite d'octets de données de service incluant la commande d'alternat de l'étape 100 ;
• étape 102 : l'opérateur parle dans le micro 14 et
• étape 103 : les intensités sonores qui en résultent sont échantillonnées à 8 kilohertz et converties en suites d'octets par le convertisseur 27 ;
• étape 104 : le module 25 emet en IP vers l'autocommutateur 9 la suite d'octets des données de service, ainsi que la suite d'octets de phonie à la vitesse de 64 kilobits par seconde via l'interface numérique 23 ;
• étape 105 : l'autocommutateur 9 reçoit cette communication simultanément avec d'autres communications émises par d'autres POC 6, il les compresse puis les rassemble en autant de groupes de trois communications destinées aux mêmes centres 2 qu'il est nécessaire pour les émettre toutes en temps réel et il multiplexe temporellement (module 41) les trois communications de chaque groupe comme expliqué précédemment pour enfin émettre tous les groupes vers les centres radio 2 à travers le réseau 3 via l'interface 11 à 64 kilobits par seconde ;
• étape 106 : le centre radio 2 reçoit la communication ci-dessus via les interfaces 11' et 34, le module 34 démultiplexant (module 51) les trois communications de chaque groupe lui parvenant et reconstituant les suites d'octets d'origine pour les transmettre au bloc 32 ;
• étape 107 : le module 35 du bloc 32 sépare les données de service des données de phonie et décompresse ces dernières, puis les transmet au bloc 37 qui les transforme en analogique à destination du terminal radio 8 ;
• étape 108 : le bloc 32 traite ensuite les données de service et commande le module 39 qui émet une commande d'alternat vers le terminal radio 8 ;
• étape 109 : sur réception du retour d'alternat d'accusé de réception transmis par le terminal radio 8 et le module 39, le bloc 32 provoque le renvoi de l'information de retour d'alternat vers le centre 1;
• étape 110 : le terminal radio 8 émet la phonie vers l'avion 4.

In the middle, on the figure 5-A , intervene a voice transmission from the center 1 to an aircraft 4 via the radio center 2. Suppose that several phonic communications are in progress between the radio center 2 and several POC 6. Then follow the following steps:

• step 100: the operator of a POC 6 controls the alternat to speak to the crew of a plane 4;
• step 101: the module 24 is a series of bytes of service data including the alternating command of step 100;
• step 102: the operator speaks in the microphone 14 and
• step 103: the resulting sound intensities are sampled at 8 kilohertz and converted into byte sequences by the converter 27;
• step 104: the IP module emets to the automatic switch 9 the sequence of bytes of the service data, as well as the sequence of voice bytes at the speed of 64 kilobits per second via the digital interface 23;
• step 105: the automatic switch 9 receives this communication simultaneously with other communications issued by other POCs 6, it compresses them and then gathers them in as many groups of three communications intended for the same centers 2 as it is necessary to transmit them all in real time and it multiplexes temporally (module 41) the three communications of each group as explained above to finally transmit all the groups to the radio centers 2 through the network 3 via the interface 11 at 64 kilobits per second;
• step 106: the radio center 2 receives the above communication via the interfaces 11 'and 34, the module 34 demultiplexing (module 51) the three communications from each group arriving and reconstructing the sequence of original bytes to transmit them to block 32;
• step 107: the module 35 of the block 32 separates the service data from the voice data and decompresses the latter, then transmits them to the block 37 which transforms them into analog for the radio terminal 8;
• step 108: the block 32 then processes the service data and controls the module 39 which transmits a command of alternation to the radio terminal 8;
• step 109: on receipt of the acknowledgment half-duplex return transmitted by the radio terminal 8 and the module 39, the block 32 causes the return of the alternate return information to the center 1;
• step 110: the radio terminal 8 transmits the voice to the aircraft 4.

• étape 200 : le pilote de l'avion 4 commande l'émission de son poste radio ;
• étape 201 : l'avion 4 émet la phonie vers le terminal radio 8 et les signaux analogiques qui en résultent sont reçus par le bloc 38 ;
• étape 202 : le terminal radio 8 reçoit l'appel de l'avion 4 et génère un appel avion vers le commutateur 39 ;
• étape 203 : le convertisseur 38 échantillonne à huit kilohertz la phonie reçue et convertit les intensités sonores qui en résultent en suite d'octets compressée à 16kb/s ;
• étape 204 : le module 36 assemble la suite d'octets des données de service et la suite d'octets de phonie compressée ;
• étape 205 : l'interface 34 effectue le multiplexage temporel (module 52) des communications en cours transitant par le centre radio 2 vers le centre de contrôle 1 et émet la communication numérique ainsi constituée vers l'autocommutateur 9 à travers le réseau 3 via les interfaces de ligne 11' et 11,
• étape 206 : l'autocommutateur 9 démultiplexe (module 42) les communications présentes dans le groupe reçu, isole la communication de la voie considérée et aiguille cette communication après décompression de la phonie, vers les POC 6 qui sont à l'écoute sur cette voie ;
• étape 207 : le module 26 du POC 6 sépare les données de service des données de phonie et transmet les données de phonie au bloc 28 et les données de service au bloc 3;
• étape 208 : le convertisseur 28 effectue la conversion numérique - analogique, à 8 kilohertz, des données de phonie reçues ;
• étape 209 : le module 24 affiche les données de service sur l'interface homme-machine 13 et
• étape 210 : le haut parleur 15 diffuse la phonie.

At the plane call, on the figure 5-B , intervenes a voice emission from the aircraft 4 to the center 1 via the radio center 2. Then follow the following steps:

• step 200: the pilot of the aircraft 4 controls the transmission of his radio;
• step 201: the aircraft 4 transmits the voice to the radio terminal 8 and the resulting analog signals are received by the block 38;
• step 202: the radio terminal 8 receives the call from the aircraft 4 and generates an aircraft call to the switch 39;
• step 203: the converter 38 samples the received voice at eight kilohertz and converts the resulting sound intensities into compressed bytes at 16kb / s;
• step 204: the module 36 assembles the sequence of bytes of the service data and the sequence of compressed speech bytes;
• step 205: the interface 34 performs the time division multiplexing (module 52) of the current communications passing through the radio center 2 to the control center 1 and transmits the digital communication thus constituted to the switch 9 through the network 3 via the line interfaces 11 'and 11,
• step 206: the automatic switch 9 demultiplexes (module 42) the communications present in the group received, isolates the communication of the channel considered and requires this communication after decompression of the voice, to the POC 6 who are listening on this way ;
• step 207: the module 26 of the POC 6 separates the service data from the voice data and transmits the voice data to the block 28 and the service data to the block 3;
• step 208: the converter 28 performs the digital-to-analog conversion, at 8 kHz, of received speech data;
• step 209: the module 24 displays the service data on the human-machine interface 13 and
• step 210: the speaker 15 broadcasts the voice.

Claims (6)

1. Method for transmitting rate-limited and half-duplex voice communications, between a ground control centre (1) located at a first communication level and cockpits (4), in phonic communication with the control centre (1), of an aeroplane (4) passing through a predetermined geographical region and constituting a third communication level, by means of radio transmission/reception centres (2) in phonic retransmission between said first and third levels, these ground radio centres (2) constituting a second communication level in digital communication (3) with said first level and in analogue radio communication (5) with said third level,
   the control centre (1) continuously selecting, at the first level, for each of the aeroplanes (4), the best radio transmission/reception centre (2) of the second level effectively used in phonic retransmission from a cockpit (4) of the third level, the selection being carried out according to the powers (P) of the analogue signals from said cockpit (4) of the third level which are received at the second level,
   the method being characterised in that:

   - at least one group (Gk) of a certain number n of cockpits (4) of the third level is associated with each centre (2) of the second level on the basis of the operation by the control centre (1) and in that the n corresponding communications between the first and second levels are multiplexed (41, 52).
2. Method according to claim 1, wherein software multiplexers (41, 52) are used which are controlled over time according to the need for phonic communications with the aeroplanes (4) in transit in the region to be controlled.
3. Method according to either claim 1 or claim 2, wherein the group (Gk) contains n multiplexed voice communications (Vk) for a packet (Pk) of multiplexed service data (S).
4. Method according to any of claims 1 to 3, wherein said service data (S) then contain at least the service data (Sk) of the n multiplexed voice communications.
5. Method according to any of claims 1 to 4, wherein the group (Gk) of the n cockpits (4) of the third level is determined at the centre (1) of the first level at the same time as at least one centre (2) of the second level is selected there, ensuring the phonic retransmission from said n cockpits (4) of the third level.
6. Method according to claim 5, wherein the power data (P) of the analogue signals received from the cockpits (4) of the third level are transmitted to the centre (1) of the first level by being included in said service data (S).

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